/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is the nsSessionStore component.
 *
 * The Initial Developer of the Original Code is
 * Simon Bünzli <zeniko@gmail.com>
 *
 * Portions created by the Initial Developer are Copyright (C) 2006
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 * Dietrich Ayala <autonome@gmail.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

/**
 * Session Storage and Restoration
 * 
 * Overview
 * This service reads user's session file at startup, and makes a determination 
 * as to whether the session should be restored. It will restore the session 
 * under the circumstances described below.
 * 
 * Crash Detection
 * The session file stores a session.state property, that 
 * indicates whether the browser is currently running. When the browser shuts 
 * down, the field is changed to "stopped". At startup, this field is read, and
 * if it's value is "running", then it's assumed that the browser had previously
 * crashed, or at the very least that something bad happened, and that we should
 * restore the session.
 * 
 * Forced Restarts
 * In the event that a restart is required due to application update or extension
 * installation, set the browser.sessionstore.resume_session_once pref to true,
 * and the session will be restored the next time the browser starts.
 * 
 * Always Resume
 * This service will always resume the session if the integer pref 
 * browser.startup.page is set to 3.
 */

/* :::::::: Constants and Helpers ::::::::::::::: */

const Cc = Components.classes;
const Ci = Components.interfaces;
const Cr = Components.results;

const CID = Components.ID("{ec7a6c20-e081-11da-8ad9-0800200c9a66}");
const CONTRACT_ID = "@mozilla.org/browser/sessionstartup;1";
const CLASS_NAME = "Browser Session Startup Service";

const STATE_RUNNING_STR = "running";

/* :::::::: Pref Defaults :::::::::::::::::::: */

// whether the service is enabled
const DEFAULT_ENABLED = true;

// resume the current session at startup just this once
const DEFAULT_RESUME_SESSION_ONCE = false;

// resume the current session at startup if it had previously crashed
const DEFAULT_RESUME_FROM_CRASH = true;

function debug(aMsg) {
  aMsg = ("SessionStartup: " + aMsg).replace(/\S{80}/g, "$&\n");
  Cc["@mozilla.org/consoleservice;1"].getService(Ci.nsIConsoleService)
                                     .logStringMessage(aMsg);
}

/* :::::::: The Service ::::::::::::::: */

function SessionStartup() {
}

SessionStartup.prototype = {

  // the state to restore at startup
  _iniString: null,

/* ........ Global Event Handlers .............. */

  /**
   * Initialize the component
   */
  init: function sss_init() {
    this._prefBranch = Cc["@mozilla.org/preferences-service;1"].
                       getService(Ci.nsIPrefService).
                       getBranch("browser.");
    this._prefBranch.QueryInterface(Ci.nsIPrefBranch2);

    // if the service is disabled, do not init 
    if (!this._getPref("sessionstore.enabled", DEFAULT_ENABLED))
      return;

    // get file references
    var dirService = Cc["@mozilla.org/file/directory_service;1"].
                     getService(Ci.nsIProperties);
    this._sessionFile = dirService.get("ProfD", Ci.nsILocalFile);
    this._sessionFile.append("sessionstore.js");
    
    // only read the session file if config allows possibility of restoring
    var resumeFromCrash = this._getPref("sessionstore.resume_from_crash", DEFAULT_RESUME_FROM_CRASH);
    if (resumeFromCrash || this._doResumeSession()) {
      // get string containing session state
      this._iniString = this._readFile(this._sessionFile);
      if (this._iniString) {
        try {
          // parse the session state into JS objects
          var s = new Components.utils.Sandbox("about:blank");
          var initialState = Components.utils.evalInSandbox(this._iniString, s);

          // set bool detecting crash
          this._lastSessionCrashed =
            initialState.session && initialState.session.state &&
            initialState.session.state == STATE_RUNNING_STR;
        // invalid .INI file - nothing can be restored
        }
        catch (ex) { debug("The session file is invalid: " + ex); } 
      }
    }
    
    // prompt and check prefs
    this._doRestore = this._lastSessionCrashed ? this._doRecoverSession() : this._doResumeSession();
    if (this._iniString && !this._doRestore) {
      this._iniString = null; // reset the state string
    }
    if (this._getPref("sessionstore.resume_session_once", DEFAULT_RESUME_SESSION_ONCE)) {
      this._prefBranch.setBoolPref("sessionstore.resume_session_once", false);
    }
    
    if (this.doRestore()) {
      // wait for the first browser window to open
      var observerService = Cc["@mozilla.org/observer-service;1"].
                            getService(Ci.nsIObserverService);
      observerService.addObserver(this, "domwindowopened", true);
    }
  },

  /**
   * Handle notifications
   */
  observe: function sss_observe(aSubject, aTopic, aData) {
    var observerService = Cc["@mozilla.org/observer-service;1"].
                          getService(Ci.nsIObserverService);

    switch (aTopic) {
    case "app-startup": 
      observerService.addObserver(this, "final-ui-startup", true);
      break;
    case "final-ui-startup": 
      observerService.removeObserver(this, "final-ui-startup");
      this.init();
      break;
    case "domwindowopened":
      var window = aSubject;
      var self = this;
      window.addEventListener("load", function() {
        self._onWindowOpened(window);
        window.removeEventListener("load", arguments.callee, false);
      }, false);
      break;
    }
  },

  /**
   * Removes the default arguments from the first browser window
   * (and removes the "domwindowopened" observer afterwards).
   */
  _onWindowOpened: function sss_onWindowOpened(aWindow) {
    var wType = aWindow.document.documentElement.getAttribute("windowtype");
    if (wType != "navigator:browser")
      return;
    
    /**
     * Note: this relies on the fact that nsBrowserContentHandler will return
     * a different value the first time it's getter is called after an update,
     * due to its needHomePageOverride() logic. We don't want to remove the
     * default arguments in the update case, since they include the "What's
     * New" page.
     *
     * Since we're garanteed to be at least the second caller of defaultArgs
     * (nsBrowserContentHandler calls it to determine which arguments to pass
     * at startup), we know that if the window's arguments don't match the
     * current defaultArguments, we're either in the update case, or we're
     * launching a non-default browser window, so we shouldn't remove the
     * window's arguments.
     */
    var defaultArgs = Cc["@mozilla.org/browser/clh;1"].
                      getService(Ci.nsIBrowserHandler).defaultArgs;
    if (aWindow.arguments && aWindow.arguments[0] &&
        aWindow.arguments[0] == defaultArgs)
      aWindow.arguments[0] = null;
    
    var observerService = Cc["@mozilla.org/observer-service;1"].
                          getService(Ci.nsIObserverService);
    observerService.removeObserver(this, "domwindowopened");
  },

/* ........ Public API ................*/

  /**
   * Get the session state as a string
   */
  get state() {
    return this._iniString;
  },

  /**
   * Determine whether there is a pending session restore.
   * @returns bool
   */
  doRestore: function sss_doRestore() {
    return this._doRestore && this._iniString != null;
  },

/* ........ Auxiliary Functions .............. */

  /**
   * Whether or not to resume session, if not recovering from a crash.
   * @returns bool
   */
  _doResumeSession: function sss_doResumeSession() {
    return this._getPref("startup.page", 1) == 3 ||
      this._getPref("sessionstore.resume_session_once", DEFAULT_RESUME_SESSION_ONCE);
  },

  /**
   * prompt user whether or not to restore the previous session,
   * if the browser crashed
   * @returns bool
   */
  _doRecoverSession: function sss_doRecoverSession() {
    // do not prompt or resume, post-crash
    if (!this._getPref("sessionstore.resume_from_crash", DEFAULT_RESUME_FROM_CRASH))
      return false;

    // if the prompt fails, recover anyway
    var recover = true;
    // allow extensions to hook in a more elaborate restore prompt
    // XXXzeniko drop this when we're using our own dialog instead of a standard prompt
    var dialogURI = this._getPref("sessionstore.restore_prompt_uri");
    
    try {
      if (dialogURI) { // extension provided dialog 
        var params = Cc["@mozilla.org/embedcomp/dialogparam;1"].
                     createInstance(Ci.nsIDialogParamBlock);
        // default to recovering
        params.SetInt(0, 0);
        Cc["@mozilla.org/embedcomp/window-watcher;1"].
        getService(Ci.nsIWindowWatcher).
        openWindow(null, dialogURI, "_blank", 
                   "chrome,modal,centerscreen,titlebar", params);
        recover = params.GetInt(0) == 0;
      }
      else { // basic prompt with no options
        // get app name from branding properties
        var brandStringBundle = this._getStringBundle("chrome://branding/locale/brand.properties");
        var brandShortName = brandStringBundle.GetStringFromName("brandShortName");

        // create prompt strings
        var ssStringBundle = this._getStringBundle("chrome://browser/locale/sessionstore.properties");
        var restoreTitle = ssStringBundle.formatStringFromName("restoredTitle", [brandShortName], 1);
        var restoreText = ssStringBundle.formatStringFromName("restoredMsg", [brandShortName], 1);
        var buttonTitle = ssStringBundle.GetStringFromName("buttonTitle");
        var cancelTitle = ssStringBundle.GetStringFromName("cancelTitle");

        var promptService = Cc["@mozilla.org/embedcomp/prompt-service;1"].
                            getService(Ci.nsIPromptService);

        // set the buttons that will appear on the dialog
        var flags = promptService.BUTTON_TITLE_IS_STRING * promptService.BUTTON_POS_0 +
                    promptService.BUTTON_TITLE_IS_STRING * promptService.BUTTON_POS_1 +
                    promptService.BUTTON_POS_0_DEFAULT;
        
        var buttonChoice = promptService.confirmEx(null, restoreTitle, restoreText, 
                                          flags, buttonTitle, cancelTitle, null, 
                                          null, {});
        recover = (buttonChoice == 0);
      }
    }
    catch (ex) { dump(ex + "\n"); } // if the prompt fails, recover anyway
    return recover;
  },

  /**
   * Convenience method to get localized string bundles
   * @param aURI
   * @returns nsIStringBundle
   */
  _getStringBundle: function sss_getStringBundle(aURI) {
    var bundleService = Cc["@mozilla.org/intl/stringbundle;1"].
                        getService(Ci.nsIStringBundleService);
    var appLocale = Cc["@mozilla.org/intl/nslocaleservice;1"].
                    getService(Ci.nsILocaleService).getApplicationLocale();
    return bundleService.createBundle(aURI, appLocale);
  },

/* ........ Storage API .............. */

  /**
   * basic pref reader
   * @param aName
   * @param aDefault
   * @param aUseRootBranch
   */
  _getPref: function sss_getPref(aName, aDefault) {
    var pb = this._prefBranch;
    try {
      switch (pb.getPrefType(aName)) {
      case pb.PREF_STRING:
        return pb.getCharPref(aName);
      case pb.PREF_BOOL:
        return pb.getBoolPref(aName);
      case pb.PREF_INT:
        return pb.getIntPref(aName);
      default:
        return aDefault;
      }
    }
    catch(ex) {
      return aDefault;
    }
  },

  /**
   * reads a file into a string
   * @param aFile
   *        nsIFile
   * @returns string
   */
  _readFile: function sss_readFile(aFile) {
    try {
      var stream = Cc["@mozilla.org/network/file-input-stream;1"].
                   createInstance(Ci.nsIFileInputStream);
      stream.init(aFile, 0x01, 0, 0);
      var cvstream = Cc["@mozilla.org/intl/converter-input-stream;1"].
                     createInstance(Ci.nsIConverterInputStream);
      cvstream.init(stream, "UTF-8", 1024, Ci.nsIConverterInputStream.DEFAULT_REPLACEMENT_CHARACTER);
      
      var content = "";
      var data = {};
      while (cvstream.readString(4096, data)) {
        content += data.value;
      }
      cvstream.close();
      
      return content.replace(/\r\n?/g, "\n");
    }
    catch (ex) { } // inexisting file?
    
    return null;
  },

/* ........ QueryInterface .............. */

  QueryInterface: function(aIID) {
    if (!aIID.equals(Ci.nsISupports) && !aIID.equals(Ci.nsIObserver) && 
      !aIID.equals(Ci.nsISupportsWeakReference) && 
      !aIID.equals(Ci.nsISessionStartup)) {
      Components.returnCode = Cr.NS_ERROR_NO_INTERFACE;
      return null;
    }
    
    return this;
  }
};

/* :::::::: Service Registration & Initialization ::::::::::::::: */

/* ........ nsIModule .............. */

const SessionStartupModule = {

  getClassObject: function(aCompMgr, aCID, aIID) {
    if (aCID.equals(CID)) {
      return SessionStartupFactory;
    }
    
    Components.returnCode = Cr.NS_ERROR_NOT_REGISTERED;
    return null;
  },

  registerSelf: function(aCompMgr, aFileSpec, aLocation, aType) {
    aCompMgr.QueryInterface(Ci.nsIComponentRegistrar);
    aCompMgr.registerFactoryLocation(CID, CLASS_NAME, CONTRACT_ID, aFileSpec, aLocation, aType);

    var catMan = Cc["@mozilla.org/categorymanager;1"].
                 getService(Ci.nsICategoryManager);
    catMan.addCategoryEntry("app-startup", CLASS_NAME, "service," + CONTRACT_ID, true, true);
  },

  unregisterSelf: function(aCompMgr, aLocation, aType) {
    aCompMgr.QueryInterface(Ci.nsIComponentRegistrar);
    aCompMgr.unregisterFactoryLocation(CID, aLocation);

    var catMan = Cc["@mozilla.org/categorymanager;1"].
                 getService(Ci.nsICategoryManager);
    catMan.deleteCategoryEntry( "app-startup", "service," + CONTRACT_ID, true);
  },

  canUnload: function(aCompMgr) {
    return true;
  }
}

/* ........ nsIFactory .............. */

const SessionStartupFactory = {

  createInstance: function(aOuter, aIID) {
    if (aOuter != null) {
      Components.returnCode = Cr.NS_ERROR_NO_AGGREGATION;
      return null;
    }
    
    return (new SessionStartup()).QueryInterface(aIID);
  },

  lockFactory: function(aLock) { },

  QueryInterface: function(aIID) {
    if (!aIID.equals(Ci.nsISupports) && !aIID.equals(Ci.nsIModule) &&
        !aIID.equals(Ci.nsIFactory) && !aIID.equals(Ci.nsISessionStartup)) {
      Components.returnCode = Cr.NS_ERROR_NO_INTERFACE;
      return null;
    }
    
    return this;
  }
};

function NSGetModule(aComMgr, aFileSpec) {
  return SessionStartupModule;
}
